This invention relates to colloidal size particulates containing particles of an inorganic material and to polymerization processes used to prepare such particulates.
Metals, metal oxides, pigments, fillers and other inorganic particulates that tend to agglomerate are often coated with or encapsulated in hydrophobic polymers. These coated or encapsulated particles are often used in a wide variety of applications such as electroconductive additives to plastics, toners in electrophotographic applications, pigmented paints as well as many other applications.
Conventionally, such particulates are prepared by (1) treating the inorganic solid with acid, a combination of acid and base, alcohol or a polymer solution; (2) dispersing an addition polymerizable monomer in an aqueous dispersion of a treated inorganic solid and (3) subjecting the resulting dispersion to emulsion polymerization conditions. Examples of such methods are described in U.S. Pat. Nos. 4,048,136; 3,383,346; 3,935,340; 3,544,500 and 3,884,871. Unfortunately, these methods are deficient in that they often require expensive multi-step procedures, anchoring agents, functional additives, stabilizing agents and the like. Also, the polymeric particulates often must be employed as viscous pastes or dry powders.
In view of the deficiencies of the prior art methods for preparing such particulates, an improved method which eliminates or substantially reduces the adverse affects of the aforementioned procedure deficiencies is highly desirable.